1. Field of the Invention
The present invention is directed to an arrangement for adjusting the tension of a thread which may be drawn from a spool by means of a thread take-off arrangement.
2. Description of Related Art
In the known arrangement of this type (DE PS 30 25 765) the control of the thread tension results from an adjustable thread brake whose frictional force may be changed in conjunction with a measuring arrangement for the thread tension placed downstream of the brake. When the measured thread tension rises, the braking action is reduced. Such arrangements are used, for example, in warping machines but also play a role in other textile machine, for example twisting machine and circular knitting machines.
German Patent Application DE OS 30 01 069 discloses a thread provision and control arrangement for a needle weaving machine for bands or similar machines wherein the threads to be processed are subjected to a weft thread tensioning cycle. For this purpose, the threads are led over thread tensioning arrangement in the form of a brake, a drum driven at a constant rate of revolution and the eyelet of a spring biased arm. In the absence of thread tension, the spring loaded arm deviates whereby the threads are brought under a clamping plate. This has the effect that the threads are no longer driven by the drum.
In warping machines, beaming machines, and other winding machines, it is customary to pull off a large number of threads often several hundred threads from spools on a creel at the same time and wind them together, wherein the thread tension for all the threads should be substantially the same and the time of winding should be substantially constant. For this reason, a thread brake is provided for each spool.
It has already been shown that in the utilization of the known friction brake, a relatively hard wind body is provided. Where thin threads are used, the danger of thread breaks exists. This is particularly true when higher warping speeds are desired (for example instead of the previous 600 meters per minute, now 1500 meters per minute). Similar disadvantages which occur because of high thread tension also occur with other textile machines.
The problem to be solved by the present invention is to provide an arrangement of the prior art which can also be utilized with a drive having a lower level of thread tension.